Atmospheric scientists often use mixing ratios to express the concentrations of trace compounds in air. mixing ratios are often expressed as ppmv (parts per million volume): ppmv of x 5 vol of x at stp 3 106 total vol of air at stp on a certain november day, the concentration of carbon monoxide in the air in downtown denver, colorado, reached 3.0 3 102 ppmv. the atmospheric pressure at that time was 628 torr and the temperature was 08c.
a. what was the partial pressure of co?
b. what was the concentration of co in molecules per cubic meter?
c. what was the concentration of co in molecules per cubic centimeter?

a)

b)

c)

Explanation:

a) The partial pressure of CO₂ is given by:

Since the molar fraction of the gas is directly proportional to the volume of the gas, the molar fraction is given by:

Hence,

b) Using the Ideal Gas Law, we can find the number of moles of CO₂:

where:

The concentration of CO in molecules per cubic meter is:

c) The concentration of CO in molecules per cubic centimeter is:

answer : a model is often used to explain and make things easier to understand when any scientific topic needs to be demonstrated and explained.

as in this case where a scientist wants to use a model to present the results of his detailed scientific investigation. he should do it as it will him to make the audience understand the concept in a much better way. also, it can be changed according to new scientific understandings.